IRON & STEEL GLOSSARY: A-B

A

Abrasive
A substance capable of removing material from another substance in machining, abrasion or polishing.

Abrasive Wear
The removal or displacement of materials from a surface when hard particles slide or roll across the surface under pressure. The particles may be loose or may be part of another surface in contact with the surface being worn.

[more...]

ACRONYMS FOR STANDARDS AND ORGANIZATIONS

ACRONYMS FOR STANDARDS AND ORGANIZATIONS

AS - Australian Standard(s)

AISC - American Institute of Steel Construction

ANSI - American National Standards Institute

API - American Petroleum Institute

ASTM - American Society for Testing and Materials

AWS - American Welding Society

BCA - Building and Construction Authority of Singapore

BS - British Standard(s)

EN - European Standard(s)

GB - National Standard(s) of the People’s Republic of China

ISO - International Organization for Standardization

JIS - Japanese Industrial Standard(s)

NZS - New Zealand Standard(s)

SINGLAS - The Singapore Laboratory Accreditation Scheme

Schedule Terminology

An introduction to pipes and the schedule terminology

For all pipe sizes the outside diameter (O.D.) remains relatively constant. The variations in wall thickness affects only the inside diameter (I.D.).
A schedule number indicates the approximate value of

Sch. = 1000 P/S

where

P = service pressure (psi)

S = allowable stress (psi)

The higher the schedule number is, the thicker the pipe is. Since the outside diameter of each pipe size is standardized, a particular nominal pipe size will have different inside pipe diameter depending on the schedule specified.

Welded and Seamless Wrought Steel Pipe

To distinguish different weights of pipe, it is common to use the Schedule terminology from ANSI/ASME B36.10 Welded and Seamless Wrought Steel Pipe:

• Light Wall
• Schedule 10 (Sch/10, S/10)
• Schedule 20 (Sch/20, S/20)
• Schedule 30 (Sch/30, S/30)
• Schedule 40 (Sch/40, S/40)
• Standard Weight (ST, Std, STD)
• Schedule 60 (Sch/60, S/60)
• Extra Strong (Extra Heavy, EH, XH, XS)
• Schedule 80 (Sch/80, S/80)
• Schedule 100 (Sch/100, S/100)
• Schedule 120 (Sch/120, S/120)
• Schedule 140 (Sch/140, S/140)
• Schedule 160 (Sch/160, S/160)
• Double Extra Strong (Double extra heavy, XXH, XXS)

Note that many of the schedules are identical in certain sizes.

Stainless Steel Pipe

For stainless steel pipes thru 12-inch, schedule numbers from Schedule 5S to schedule 80S are used as published in ANSI/ASME 36.19M Stainless Steel Pipe.

• Schedule 5S (Sch/5S, S/5S)
• Schedule 10S (Sch/10S, S/10S)
• Schedule 40S (Sch/40S, S/40S)
• Schedule 80S (Sch/80S, S/80S)

Source: http://www.engineeringtoolbox.com/pipe-schedules-d_557.html

Mechanical Properties of Metals

1. Introduction

Often materials are subject to forces (loads) when they are used. Mechanical engineers calculate those forces and material scientists how materials deform (elongate, compress, twist) or break as a function of applied load, time, temperature, and other conditions.

Materials scientists learn about these mechanical properties by testing materials. Results from the tests depend on the size and shape of material to be tested (specimen), how it is held, and the way of performing the test. That is why we use common procedures, or standards, which are published by the ASTM.

2. Concepts of Stress and Strain

Stress vs. Strain curve typical of aluminum
1. Ultimate Strength
2. Yield strength
3. Proportional Limit Stress
4. Tensile strength
5. Offset Strain (typically 0.2%).

To compare specimens of different sizes, the load is calculated per unit area, also called normalization to the area. Force divided by area is called stress. In tension and compression tests, the relevant area is that perpendicular to the force. In shear or torsion tests, the area is perpendicular to the axis of rotation.

s = F/A0 tensile or compressive stress

t = F/A0 shear stress

The unit is the Megapascal = 106 Newtons/m2.

There is a change in dimensions, or deformation elongation, DL as a result of a tensile or compressive stress. To enable comparison with specimens of different length, the elongation is also normalized, this time to the length L. This is called strain, e.

e = DL/L

The change in dimensions is the reason we use A0 to indicate the initial area since it changes during deformation. One could divide force by the actual area, this is called true stress (see Sec. 6.7).

For torsional or shear stresses, the deformation is the angle of twist, q (Fig. 6.1) and the shear strain is given by:

g = tg q

3. Stress—Strain Behavior

Elastic deformation. When the stress is removed, the material returns to the dimension it had before the load was applied. Valid for small strains (except the case of rubbers).

Deformation is reversible, non permanent

Plastic deformation. When the stress is removed, the material does not return to its previous dimension but there is a permanent, irreversible deformation.

In tensile tests, if the deformation is elastic, the stress-strain relationship is called Hooke's law:

s = E e

That is, E is the slope of the stress-strain curve. E is Young's modulus or modulus of elasticity. In some cases, the relationship is not linear so that E can be defined alternatively as the local slope:

E = ds/de

Shear stresses produce strains according to:

t = G g

where G is the shear modulus.

Elastic moduli measure the stiffness of the material. They are related to the second derivative of the interatomic potential, or the first derivative of the force vs. internuclear distance (Fig. 6.6). By examining these curves we can tell which material has a higher modulus. Due to thermal vibrations the elastic modulus decreases with temperature. E is large for ceramics (stronger ionic bond) and small for polymers (weak covalent bond). Since the interatomic distances depend on direction in the crystal, E depends on direction (i.e., it is anisotropic) for single crystals. For randomly oriented policrystals, E is isotropic.

4. Anelasticity

Here the behavior is elastic but not the stress-strain curve is not immediately reversible. It takes a while for the strain to return to zero. The effect is normally small for metals but can be significant for polymers.

5. Elastic Properties of Materials

Materials subject to tension shrink laterally. Those subject to compression, bulge. The ratio of lateral and axial strains is called the Poisson's ratio n.

n = elateral/eaxial

The elastic modulus, shear modulus and Poisson's ratio are related by E = 2G(1+n)

6. Tensile Properties

Yield point. If the stress is too large, the strain deviates from being proportional to the stress. The point at which this happens is the yield point because there the material yields, deforming permanently (plastically).

Yield stress. Hooke's law is not valid beyond the yield point. The stress at the yield point is called yield stress, and is an important measure of the mechanical properties of materials. In practice, the yield stress is chosen as that causing a permanent strain of 0.002 (strain offset, Fig. 6.9.)

The yield stress measures the resistance to plastic deformation.

The reason for plastic deformation, in normal materials, is not that the atomic bond is stretched beyond repair, but the motion of dislocations, which involves breaking and reforming bonds.

Plastic deformation is caused by the motion of dislocations.

Tensile strength. When stress continues in the plastic regime, the stress-strain passes through a maximum, called the tensile strength (sTS) , and then falls as the material starts to develop a neck and it finally breaks at the fracture point (Fig. 6.10).

Note that it is called strength, not stress, but the units are the same, MPa.

For structural applications, the yield stress is usually a more important property than the tensile strength, since once the it is passed, the structure has deformed beyond acceptable limits.

Ductility. The ability to deform before braking. It is the opposite of brittleness. Ductility can be given either as percent maximum elongation emax or maximum area reduction.

%EL = emax x 100 %

%AR = (A0 - Af)/A0

These are measured after fracture (repositioning the two pieces back together).

Resilience. Capacity to absorb energy elastically. The energy per unit volume is the

area under the strain-stress curve in the elastic region.

Toughness. Ability to absorb energy up to fracture. The energy per unit volume is the total area under the strain-stress curve. It is measured by an impact test (Ch. 8).

7. True Stress and Strain

When one applies a constant tensile force the material will break after reaching the tensile strength. The material starts necking (the transverse area decreases) but the stress cannot increase beyond sTS. The ratio of the force to the initial area, what we normally do, is called the engineering stress. If the ratio is to the actual area (that changes with stress) one obtains the true stress.

8. Elastic Recovery During Plastic Deformation

If a material is taken beyond the yield point (it is deformed plastically) and the stress is then released, the material ends up with a permanent strain. If the stress is reapplied, the material again responds elastically at the beginning up to a new yield point that is higher than the original yield point (strain hardening, Ch. 7.10). The amount of elastic strain that it will take before reaching the yield point is called elastic strain recovery (Fig. 6. 16).

9. Compressive, Shear, and Torsional Deformation

Compressive and shear stresses give similar behavior to tensile stresses, but in the case of compressive stresses there is no maximum in the s-e curve, since no necking occurs.

10. Hardness

Hardness is the resistance to plastic deformation (e.g., a local dent or scratch). Thus, it is a measure of plastic deformation, as is the tensile strength, so they are well correlated. Historically, it was measured on an empirically scale, determined by the ability of a material to scratch another, diamond being the hardest and talc the softer. Now we use standard tests, where a ball, or point is pressed into a material and the size of the dent is measured. There are a few different hardness tests: Rockwell, Brinell, Vickers, etc. They are popular because they are easy and non-destructive (except for the small dent).

11. Variability of Material Properties

Tests do not produce exactly the same result because of variations in the test equipment, procedures, operator bias, specimen fabrication, etc. But, even if all those parameters are controlled within strict limits, a variation remains in the materials, due to uncontrolled variations during fabrication, non homogenous composition and structure, etc. The measured mechanical properties will show scatter, which is often distributed in a Gaussian curve (bell-shaped), that is characterized by the mean value and the standard deviation (width).

12. Design/Safety Factors

To take into account variability of properties, designers use, instead of an average value of, say, the tensile strength, the probability that the yield strength is above the minimum value tolerable. This leads to the use of a safety factor N > 1 (typ. 1.2 - 4). Thus, a working value for the tensile strength would be sW = sTS / N.

Important Terms:

Anelasticity
Ductility
Elastic deformation
Elastic recovery
Engineering strain
Engineering stress
Hardnes
Modulus of elasticity
Plastic deformation
Poisson’s rati
Proportional limit
Shear
Tensile strength
Ultimate strength
Toughness
Yielding
Yield strength

Not tested: true stress-true stain relationships, details of the different types of hardness tests, but should know that hardness for a given material correlates with tensile strength. Variability of material properties.

Read more:
+ http://www.virginia.edu/bohr/mse209/chapter6.htm
+ http://en.wikipedia.org/wiki/Tensile_strength

Bolt Glossary

AASHTO The American Association of State Highway and Transportation Officials oversees the advancement of transportation policies and standards for the industry.
anchor bolt A steel rod or bar with one end intended to be embedded in concrete and the other end threaded and projected for anchoring material to concrete. The end cast in concrete may be straight, bent hook, a forged head, or welded attachment to resist forces imposed on the anchor bolt.
annealing Describes the process of heating and cooling steel to soften hardness caused by manufacturing or previous heat treating.
ASTM American Society for Testing and Materials, is a leading standards development organization. Portland Bolt participates as a voting member on ASTM Committee F16 on Fasteners. This committee has jurisdiction on over 60 fastener standards.
average coating thickness This is determined as either the value obtained by analytical methods or the mean value of a specified number of local thickness measurements that are evenly distributed over the significant surface.
bar This describes carbon and alloy steel bar that is produced from hot rolled or cast billets with the cross sectional dimensions that have a relatively constant dimension.
bearing-type connection A bolted connection that assumes that shear forces are transmitted by the bolt bearing against the sides of the holes in the connected material. Often denote on drawings with an “X” (i.e. A325-X) which excludes threads from the shear plane or “N” (i.e. A325-N) which includes threads in the shear plane.
bend test This test is meant to determine the toughness or ductility of a fastener. It is usually performed by bending the fastener through its axis or on a round mandrel.
bolt A headed and externally threaded fastener designed to be assembled with a nut.
brinell hardness testing This is a common method of determining the hardness of metal products. A test is conducted by forcing a carbide ball indenter into the surface of the test specimen. The resulting indentation is measured and the brinell hardness number is calculated by using a formula that divides the test force by the indentation. Standards for this test are defined under ASTM E10.
cap screw A fastener manufactured by cold forming, with tighter dimensional tolerances than a hot forged bolt.
carbon steel A metal alloy that principle elements are carbon and iron. Contains other trace elements in undetectable amounts.
certification A procedure and action to verify in writing a process or material meets a set of applicable standards. This helps ensure consist products for both manufacturer and end users.
clamp load Also called initial load or preload, is created when tension is applied on a bolt and results in equal force and measures of the compression of two parts. It is commonly calculated as 75% of minimum proof load.
cold forming Processing material by forcing metal through various dies, below the recrystallization temperature. Most mass produced fasteners use this technique and require large production runs with long lead times.
compression load The load which tends to compress or shorten the member. The value for compressive strength may depend upon the degree of distortion.
corrosion resistance This describes the ability of a fastener to resist corrosion under specified conditions. Hot dip galvanizing is a cost effective way to provide a high level of corrosion protection for a variety of applications and environmental conditions.
cut thread A threading method produced by removing material from the surface with a form cutting tool.
destructive test A test to determine the mechanical properties of a material or the behavior of an item which results in the destruction of the sample or item.
distributor A person or organization who purchases fasteners for the purpose of reselling them. They will typically specialize in a certain industry and carry standard fasteners. A distributor may or may not alter the fasteners prior to resale.
ductility (externally threaded fasteners) The measure of a fastener's ability to deform prior to the point of fracturing. Machined test pieces are made to evaluate the metal's elongation and reduction of area. The lower the ratio of its specified minimum yield strength to its specified minimum tensile strength, the greater the fastener's ductility.
elongation Measures the change in length based on a percentage of the original size.
extensometer This device measures the linear deformation of a fastener to sense the elongation under tensile stress in a controlled test environment.
eye bolt A bolt having one end which is a closed or open ring with a threaded shank.

 

eye bolt

fastener A mechanical device that holds or joins two or more components in definite positions with respect to each other and is often described as a bolt, nut, rivet, screw, washer, or special formed part.
fastener identification marking A stamp, paint, or other permanent identifier that may include manufacturer information and applicable grade markings for certification purposes.
fastener manufacturer An organization that fabricates raw steel into a fastener meeting specified standards.
fastener quality A fastener's adherence to its specification for dimensional tolerances, mechanical properties, and other requirements stated under applicable standards.
fastener specification A precise statement of set requirements to be satisfied by a fastener, its material, or its processing. It also indicates the procedure used to determine whether the requirements given are satisfied. This would include specifications like ASTM A194, A449, F1554 and SAE Grade 2.
fastener standard A document which details the attributes of a finished fastener and includes such characteristics as geometry, material or chemistry, heat treatment, finish, testing lot size, and packaging. Examples would include organization like: Industrial Fastener Institute (IFI) and American National Standards Institute (ANSI).
fastener testing A determination or verification that the fastener meets its specification requirements.
forging The process of forming raw steel into specified shapes. Some examples of forged products would be hex bolts, clevises, and barrier pins.

clevis

forging cracks This may occur during fastener manufacturing at the cutting or forging operations and are located on the top of the head or on the raised periphery of indented head bolts.
galling This can happen when a stainless steel fastener is tightened, the thin oxide layer on the surface of the steel may scrape off resulting in the nut and washer welding together. When disassembled, the welded material may be torn and pitted.
gimlet point A term that describes a cone point that is threaded completely along the 45 to 50 degree point and is commonly found on lag screws.
grade identification symbols Permanent markings denoting the specification used to manufacture a fastener. This would indicate the appropriate material, mechanical properties and other criteria used to produce the bolt.
heat analysis A chemical analysis of a given heat by the producer, which determines the percentages of its elements.
heat resistance This describes the extent to which a bolt retains specified properties as measured by exposure of the material to a certain temperature and environment for a specified time.
hex bolt This refers to a bolt made to ANSI B18.2.1 and has different tolerances than hex cap screw.
high strength bolts A term which is used commercially to denote ASTM A325 or A490 bolts which are primarily used in construction applications.
high temperature bolts Bolts specifically manufactured from high temperature alloys to maintain tensile loads at temperatures between 500°F and 1800°F. Refer to ASTM A193 for more information.
hot-dip galvanizing The process of the immersion of fasteners in a bath of molten zinc for a controlled time period to obtain specified coating weight or thickness. This is a cost effective method for creating highly corrosive resistant steel products.
hydrogen embrittlement The process by which high strength steel becomes brittle and fractures following absorption of hydrogen. There is a danger of this occurring when attempting to zinc coat high strength bolts (e.g. ASTM A490, ASTM A354 BD). This can occur during the acid washing process prior to galvanizing.
IFI The Industrial Fasteners Institute is the trade association of the North American fastener manufacturing industry. It is a strong supporter of fastener standards and partners ASTM, ASME, SAE and other organizations to develops specifications. The Inch Fastener Standards (2003) is leading reference guide for mechanical fasteners technical data.
machined specimen This is a test specimen machined from a full-size fastener to specific dimensions to standardize test results; often specified when a full-size fastener cannot be reasonably or practically tested. This test is used to determine elongation and reduction of area.
material test report A document verifying the raw material meets specified requirements and includes results of mechanical tests and chemical analyses.
mechanically galvanized Describes a coating technique of applying cold zinc powder to bolts by either cold welding or barrel finishing.
mechanical properties The fastener characteristics which relate to its reaction to applied loads; these properties may be those of the basic raw material or result from the manufacturing process.
nut An internally threaded product intended for use on external or male screw threads such as a bolt or a stud for the purpose of tightening or assembling two or more components.
passivation The process of forming an oxide film on the surface of stainless steel by chemical treatment to improve corrosion resistance of stainless steel fasteners. This process is usually done after the steel has been subjected to thermal treatment (i.e. hot forging).
pickle The process of removing surface oxides by chemical means.
plain Describes a fastener that is free of additional coatings or finishes like zinc, hot-dip galvanizing, or paint. Also referred to as "black."
proof load (externally threaded fastener) The tension applied load that a fastener must withstand without any indication of permanent deformation or failure. Proof load is typically calculated at 90-93% of the minimum yield strength.
proof load (internally threaded fastener) The axially-applied load using a bolt or threaded mandrel that must be supported by a nut without indication of thread stripping or failure.
proof stress load The proof stress is the amount of stress (on a stress -strain curve) where a material will exceed the elastic/plastic limit. In other words, it begins to get a permanent set on further stressing. The 0.2% is the offset from the normal stress/strain curve ( a line drawn parallel to the normal curve - offset 0.2% of strain).
quench The process during heat treatment of submerging steel in a liquid medium to rapidly cool it, typically in water or oil.
quench cracks Surface discontinuities in an irregular or erratic pattern on the surface of the fastener which may occur because of excessive thermal or transformation stresses during fastener heat treatment.
reduced diameter body A fastener having a body diameter not less than the minimum pitch diameter of its thread nor more than its minimum full body diameter.
reduction of area The difference between the original cross sectional area of a tensile test specimen and its minimum cross section after the test sample has fractured.
roll thread The threading method that uses dies to displace rather than remove material in order to create threads. Often used in conjunction with reduced diameter body.
rotational capacity test "rocap" A test in which a bolt is assembled in a steel joint or tension measuring device with a lubricated nut, and tightened to not less than 10% of the bolt proof load. After initial tightening, the nut is rotated through specified degrees of rotation, and torque values are obtained to assure proper performance.
SAE Society of Automotive Engineers specification's cover fasteners typically used in automotive, equipment, and machinery applications.
screw A mechanical fastener designed to thread by turning the head into a tapped hole or to form its own threads during installation.
shear strength A maximum load applied to a fastener’s axis that can be withstood prior to failure.
shear stress area An area perpendicular to the fastener axis which is based on the root diameter (minor diameter) of an externally threaded bolt or screw.
slip-critical connection The high-strength bolt clamps the connected parts in such a way that the shearing force is resisted by the friction between the parts, not by the shear on the body of the bolts. This is often denoted on drawings as “SC” (i.e. A325-SC).
stainless steel A steel which has as its primary alloying element, chromium ranging from 10% to 30%. Other alloying elements such as nickel and molybdenum may also be added.
strain hardening An increase in strength and hardness resulting from the cold working of steel. This is also referred to as work hardening.
stress relief annealing A heating process applied to forged/headed fasteners to relieve any mechanical stresses generated during the forming process.
structural bolt A heavy hex head bolt intended for use in structural applications. Most commonly graded as ASTM A325 or A490.
surface discontinuities Irregularities of a fastener. These may include cracks, head bursts, shear bursts, seams, folds, thread laps, voids, tool marks, and nicks or gouges.
tap bolt A bolt that is threaded to the under the head. ANSI compliant tap bolts are made to the same tolerances as hex cap screws.
tensile strength The maximum tensile-applied load a fastener can hold prior to facture.
test report A written or electronic document provided by the authorized party to certify that a tested fastener's chemical and mechanical properties conform to the specification required.
thread galling The displacement of material between mating threads during tightening, which causes contact points to shear, producing friction, increased resistance to tightening, and even seizing of the threads. Thread galling is most common with fasteners made of materials that self-generate an oxide surface film such as stainless steel.
tie rod A piece of steel typically threaded on each end used in an assembly with clevises and turnbuckles, often used to support canopies, awnings and other building structures.

tie rod end

traceability The capability to authenticate manufacturing history by documentation of raw material, heat number, locations, or application of the product.
ultimate tensile load The maximum tensile-applied load a fastener can support prior to fracture, and normally expressed in terms of pounds per square inch (psi) or pounds-force (lbf).

Source: www.portlandbolt.com